Electronic devices such as optoelectronic devices are frequently formed in assemblies which contain components which are arranged in multilayer structures. There is therefore a need for structures comprising angled transitions to connect electronic components located in layers of differing heights. For example, surface mounted devices are typically powered via electrical connections which pass through a package body to connect radiofrequency transmission layers disposed on opposing faces of the package body. Commonly, the electrical connection may be orthogonal to the radiofrequency transmission layers, resulting in a pair of angled transitions of 90°.
Such angled transitions are known to be problematic for high performance radiofrequency (RF) devices. In particular, angled transitions comprising interconnections to a circuit or radiofrequency transmission layer housed within a package may require careful impedance matching to ensure high RF performance.
Several techniques and materials are known in the art for forming structures with angled transitions. Ceramic materials may be used as a supporting structure for the radiofrequency transmission layers, in which case electrical connections can be located in holes through the ceramic material. Alternatively, U.S. Pat. No. 7,484,900 describes conductors bent within a plastic material to realise a transition between internal and external conducting layers in an optoelectronic device. The bending of the conductors avoids inductance parasitic effects which may degrade the radiofrequency performance.
A further approach for forming angled transitions uses a coaxial glass bead mounted within the package body. The coaxial glass bead comprises an insulating glass cylinder with a central conducting pin which may be connected to a radiofrequency transmission layer by soldering. This approach has the advantage that a metal package body can be used and frequently results in good radiofrequency performance. Unfortunately, the approach can suffer from problems related to tolerances and process control, particularly when multiple circuits must be interconnected simultaneously.
The skilled person would therefore understand the desirability of an improved angled transition that is suitable for use in high performance RF devices.